In various rotating machines including a compressor, a turbine, and the like, lubricating oil is supplied to bearings supporting a rotor. Each of the bearings forms an oil film between the rotor and itself with the lubricating oil, and supports the rotor without restraining the rotation of the rotor.
For example, in a centrifugal compressor disclosed in Patent Document 1, a shaft, which is a rotor, is supported by journal bearings and thrust bearings. The centrifugal compressor is provided with a gas seal. The gas seal seals a gap between the rotor and a casing so that working fluid flowing in a flow passage formed in the casing serving as a stator does not leak to the outside of the casing.
The above-mentioned gas seal includes a rotating ring and a stationary ring. The rotating ring is provided integrally with the rotor. The stationary ring is fixed to the casing, and is provided so as to oppose the rotating ring in the axial direction of the rotor. The stationary ring is pushed against the rotating ring by a coil spring or the like. Accordingly, the stationary ring and the rotating ring are brought into contact with each other so as to push each other in a state in which the rotating machine is stopped. Further, a groove is formed on the surface of the rotating ring opposite to the stationary ring. In a case in which the rotating machine is operated and a rotating shaft is rotated in a state in which seal gas is supplied, the seal gas is introduced between the rotating ring and the stationary ring by the groove. The stationary ring is pushed against the biasing force of the coil spring in the axial direction of the rotor by the pressure of the seal gas. As a result, a small gap is formed between the rotating ring and the stationary ring. The seal gas is supplied to the gap, so that a gap between the rotor and the casing is sealed.
In a sealing device, such as the above-mentioned gas seal, liquid, such as lubricating oil, used for a bearing or the like needs to be made not to enter the gap of a gas sheath to ensure sealing performance. For this purpose, another sealing device, such as a labyrinth seal, is provided between the bearing and the gas seal. In another sealing device, a sealing body provided with a labyrinth seal or the like is fixed to a stator such as a casing.